Generally, if a vehicle is stopped outdoors for a given period of time (e.g., 8 hours or longer), the engine temperature drops to the ambient temperature. In order to prevent the engine temperature from falling to the ambient temperature, a heat retention member comprised of an upper lid part covering the engine from above and side-wall parts covering the sides of the engine may be provided. The heat retention member suppresses the drop of the engine temperature, makes a restart of the engine possible from the highest possible temperature, reduces the fuel injection amount during an engine warm-up, improves fuel consumption, makes a quick engine warm-up possible, and keeps engine oil warm. Therefore, a temperature drop of the engine oil can be suppressed, and a slide resistance of the engine oil can also be reduced. That is, the heat retention member can achieve both the quick engine warm-up (an improvement in fuel consumption) and the reduction in the slide resistance of the engine oil.
JP2013-119384A discloses an engine encapsulation structure of a vehicle which includes a dedicated covering member (a heat retention member) covering the engine from above and the side. However, as JP2013-119384A does not disclose how to reduce the weight and the cost of the covering member, there is room for improvement.